The administration of gas, and particularly oxygen, to a patient is often lax and/or unsatisfactory. The administration, regulation, and efficiency are very poor since a relatively unknown volume of oxygen is delivered to the patient. For the most part, a simple oxygen mask or a nasal cannula of one type or another is normally used for the routine administration of oxygen.
A wide variety of oxygen masks have been available, varying in construction, style, and material, depending upon the specific purpose for which each is desired to be employed. Until recently, most masks were made of rubber. As a result of the need to provide a mask which is inexpensive, requires little storage space, need not be sterilized, and can be disposed of after each use to minimize contamination, most oxygen masks presently in use are made of plastic.
The basic mask which is available today uses neither a valve nor a reservoir bag. Exhaled air from the lungs of the patient is usually vented through holes in the body of the mask. In view of its convenience and relative comfort, the basic mask is widely used whenever moderate oxygen concentrations are desired for short periods of time. This might occur, for example, during the postoperative recovery state of a patient. Such a mask might also be used, for example, during either temporary or interim therapy when a patient is being weaned from continuous oxygen administration.
Most masks available today are relatively crude, causing a prediction of the exact volume of oxygen delivered to the patient to be impossible. However, it is known that the delivered concentrations vary from 35% to 55%, at gas flow rates of 6 to 10 liters per minute.
The nasal cannula is an appliance which normally includes two tips which extend from an oxygen supply tube and are inserted into the nostrils of a patient. The cannula can be held in place by head straps or by bows that hook over the ears, in the manner of eye glasses.
Unfortunately, the cannula suffers from the disadvantage of being instable, i.e., it is easily dislodged from a restless or unobservant patient. While a doctor or nurse making medical rounds might note that an oxygen flow meter is open, he or she might not notice that the cannula is so twisted out of place that the patient could not get any significant amount of oxygen.
The cannula also suffers from the disadvantage that it is often necessary to pay attention to a patient's comfort when instituting oxygen treatment. An excessive flow rate of oxygen, the definition of which varies according to the patient, can produce a considerable amount of pain in the frontal sinuses of the patient. Also, such nasal pathology as a deviated septum, mucosal edema, mucus drainage, and polyps may interfere with a patient's oxygen intake.
In those cases in which a naso-gastric tube might be used together with the nasal cannula, the utility of the latter is further degraded. In addition to dislodgement problems, the combined affect of the two tubes placed in one nostril creates a physical irritant to the delicate mucosal tissues of the nasal passage and sinuses. Such irritation often takes the form of ulcerative lesions. Since a decreased volume of oxygen is often experienced during the use of the two tubes, the normal procedure is to increase the rate of oxygen flow. However, that often results in the desiccation of tissues, further traumatizing them, causing severe frontal sinus pain and various pathalogic results.
Consequently, it is believed that the basic oxygen mask having a body which is pressed against the face of the patient is far superior to the nasal cannula for the application of oxygen. Nevertheless, such masks suffer from the disadvantage that, in many postoperative and related cases, a naso-gastric intubation procedure is necessary. In such a case, plastic tubing is usually inserted into the patient's nasal passageway and guided down the esophagus into the upper gastric area. This tubing is an obstruction, as far as the administration of oxygen is concerned, and complicates the application of the mask or the cannula.
If, today, a naso-gastric tube and an oxygen mask are to be used simultaneously, the tube is put in place first and the mask is then applied. The seal of the mask against the face of the patient is incomplete due the protrusion of the tube at the point that the tube intersects the body of the mask. In other words, it is impossible to conform the mask to the facial configuration of the patient and, in many cases, the mask is generally askew. Such incorrect seating of the mask allows oxygen to freely pass to the atmosphere, resulting in treatment of the patient with a decreased and uncontrolled volume.
Additionally, the stability of the mask as well as the patient's comfort are complicated by the tube. The mask is much less secure and more easily dislodged by an unobservant, restless, or mobile patient. Also, the tube is usually placed across and secured to the facial skin in an attempt to prevent relative movement among the patient, tube, and mask. The taping of the tube to the skin often produces discomfort and runs the risk of producing a pressure necrosis of the skin.
An example of a prior art mask which may be used together with a naso-gastric tube in the manner described above has been illustrated in U.S. Pat. No. 3,357,426 to Cohen. The drawings of that patent clearly depict the manner in which the naso-gastric tube is located on the face of the patient in such a manner as to prevent a complete seal about the edge of the mask body, rendering the mask less stable on the face of the patient.
On the other hand, U.S. Pat. No. 3,809,079 to Buttaravoli discloses a combined resuscitation mask and airway for ventilation of a patient's lungs in a positive and reliable manner. However, that disclosure includes a rigid body which may extend down the throat of the patient; it does not relate to a structure which would facilitate a naso-gastric intubation.
Consequently, a need currently exists for a oxygen-administration device which may be simultaneously employed with a naso-gastric tube in such a manner that the volume of oxygen can be controlled at least to the same extent as may be attained with a fully seated oxygen mask.